Boundary layer relaminarization design by using an ellipsoid dome and a core of a wingtip vortex for a lift-generating body

Abstract

A boundary layer relaminarization design uses an ellipsoid dome (7) and a wingtip vortex core for a lift-generating body. Holes or slots (6), connected to a core or center of a wingtip vortex of the lift-generating body via a plenum (9) and an ellipsoid dome (7) with its outlet (8) sticking out from a surface (1) experiencing low pressure, relaminarized the boundary layer to reduce the drag. Thus, with a laminar boundary layer, the lift is increased while the drag is reduced.

Description

[0001] TITLE OF THE INVENTION

[0002] BOUNDARY LAYER RELAMINARIZ ATION DESIGN BY USING AN ELLIPSOID DOME AND A CORE OF A WINGTIP VORTEX FOR A LIFT-GENERATING BODY

[0003] BACKGROUND OF THE INVENTION

[0004] A boundary layer surrounds any body in motion in a fluid. The viscous forces present at the body's surface are at the boundary layer's origin. The amount of form and skin friction drags are determined by the behavior of the boundary layer. The skin friction drag increases from a laminar to a turbulent boundary layer. The form drag augments when there is a flow separation with a reverse flow region in the boundary layer. Thus, controlling the boundary layer by sucking a part of it and relaminarizing it allows a reduction in skin and form drags. Also, an enhancement in the generation of lift is observed.

[0005] However, boundary layer relaminarization requires a significant amount of power. The system's design must efficiently generate a low-pressure area to ingest a significant part of the boundary layer. Thus, any reverse flow within the system must be prevented.

[0006] BRIEF SUMMARY OF THE INVENTION

[0007] The present invention generally provides a design to reduce form and skin friction drags on any lift-generating body. Also, it enhances lift production by controlling the thickness of the boundary layer via suction holes or slots present on the surface of the lift-generating body. The suction force is provided by the low-pressure area resulting from the interaction between a specific geometric shape and the core or center of a lift-generating body's wingtip vortex. The holes or slots located on the lift-generating body's surfaces are connected to the low-pressure area present in the wingtip vortex core via a plenum embedded in the lift-generating body and an ellipsoid dome with a specific location on the upper surface near the tip. When the lift is

[0008] SUBSTITUTE SHEET (RULE 26) produced, the pressure gradient between the lift-generating body's surfaces leads to a vortex formation at the lift-generating body's tip. The vortex is created by the fluid's motion from the high-pressure area on one surface of the lift-generating body called the intrados to the low- pressure area on another surface of the lift-generating body called the extrados. That vortex will create an area of low pressure, which is strongest at its center, called the core. Experiments have demonstrated that the core moves onto the upper surface and achieves minimum pressure at a distance from the surface and the trailing edge near the tip.

[0009] STATE OF PRIOR ART

[0010] US 6 948 906 B2 disclosed a rotor blade system with reduced blade vortex interaction noise. The rotor blade's tip portion has slots connected through channels to holes at the leading edge. Such configuration allows part of the flow to pass from the blade's leading edge through the channels and be expelled from the rotor blade tip face.

[0011] The present invention differs from US 6 948 906 B2 because the tip is closed. No slot or opening is located at the tip. Furthermore, the pressure is not minimal at the tip but in the vortex's core situated at a distance from the upper surface near the tip and the trailing edge. Contrary to the present invention, US 6 948 906 B2 does not use the wingtip vortex core low-pressure area. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0012] SUBSTITUTE SHEET (RULE 26) EP 2 631 175 A2 disclosed an adaptive rotor blade system with multiple rotor blades composed of flaps, air outlets, or jet tip outlets. An outlet may be placed at the blade tip of one or more rotor blades.

[0013] The present invention differs from EP 2 631 175 A2 because no outlet is placed at the blade tip. No slot or opening is located at the tip. Contrary to the present invention, EP 2 631 175 A2 does not use the wingtip vortex core low-pressure area. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0014] US 7 354 247 B2 disclosed a blade for a wind energy turbine system's rotor to influence the aerodynamic boundary layer around the blade in an air stream. The blade has upper and lower opposite faces, opposite leading and trailing edges, which generates pressurized air that is discharged into the air around the upper or lower faces.

[0015] The present invention differs from US 7 354247 B2 because there are no means for generating pressurized air discharged into the atmosphere surrounding the blade. Contrary to the present invention, US 7 354 247 B2 does not use the wingtip vortex core low-pressure area.

[0016] Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow. JPH 081 331 88A disclosed a

[0017] 3

[0018] SUBSTITUTE SHEET (RULE 26) resistance-reducing device for a wing with an opening at the wing's tip connected through a pipe to pressure-adjusting chambers and suction holes placed in the wing's shell.

[0019] The present invention differs from JPH 081 331 88A because the tip is closed. No slot or opening is located at the tip. Furthermore, the pressure is not minimal at the tip but in the vortex core present at a distance from the upper surface near the tip and the trailing edge. Contrary to the present invention, JPH 081 331 88A does not use the wingtip vortex core low-pressure area. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0020] CH 209 491A disclosed a rotating cross-engine body with an automatic boundary layer system. The boundary layer is removed by centrifugal action through an opening placed at a wingtip.

[0021] The present invention differs from CH 209491A because the tip is closed. No slot or opening is located at the tip. Furthermore, the pressure is not minimal at the tip but in the vortex core situated at a distance from the upper surface near the tip and the trailing edge. Contrary to the present invention, CH 209 491 A does not use the wingtip vortex core low-pressure area. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0022] 4

[0023] SUBSTITUTE SHEET (RULE 26) US 20200339248A1 disclosed a boundary layer suction design using a wingtip vortex for a liftgenerating body that has optimized aerodynamic performances. Holes or slots connected to the tip of the lift-generating body via a plenum sucked a part of the boundary layer to delay flow transition or separation.

[0024] The present invention differs from US 20200339248A1 because the tip is closed. No slot or opening is located at the tip. Furthermore, the pressure is not minimal at the tip but in the vortex core situated at a distance from the upper surface near the tip and the trailing edge. Contrary to the present invention, US 20200339248A1 does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0025] US 2650781 A disclosed an invention related to improvements in aircraft and, more particularly, boundary layer control means for improving the efficiency of aircraft lift surfaces.

[0026] The present invention differs from US 2650781 A because US 2650781 A does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. US 2650781 A has an outlet facing backward at the trailing edge where the pressure is not minimal, and a reverse flow region is present, raising the ambient pressure that makes it difficult to suck a boundary layer. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle

[0027] 5

[0028] SUBSTITUTE SHEET (RULE 26) at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0029] US 6203269B1 disclosed helicopter rotor blades, gas turbine engine fan blades, air-moving machinery fan blades, and the like have an air inlet near the hub of the blade, which may be on the pressure side of the blade and / or near the leading edge or trailing edge nearer the tip of the blades, with an air plenum between the air inlet and the slots, whereby air is forced into the inlet, through the plenum and out of the slots into the flow adjacent the blades.

[0030] The present invention differs from US 6203269B1 because US 6203269B1 does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0031] US 20100116943A1 disclosed an aircraft component, such as a wing, has perforations through an outer wall for boundary layer suction. In the space between the outer wall and inner wall partition walls form pressure channels and suction channels that are adjacent and alternate, which communicate with the perforations. For example, alternating channels may be formed by a corrugated structure having trapezoidal corrugations providing a larger area for the suction channels than for the pressure channels. The pressure channels may be coupled to a hot-air reservoir by a control device, lines, and valves, and the suction channels may be coupled to a vacuum reservoir unless a short-circuit valve is used to cross-connect the lines.

[0032] SUBSTITUTE SHEET (RULE 26) The present invention differs from US 20100116943A1 because US 20100116943A1 does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0033] US 2973922A disclosed an invention that tends to reduce objectionable noise produced by the jet during flight.

[0034] The present invention differs from US 2973922A because US 2973922A does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0035] US 7048230B2 disclosed an invention that relates to a laminar flow nacelle for an aircraft engine, particularly to a laminar flow nacelle for a gas turbine engine and to a laminar flow nacelle for a turbofan gas turbine engine.

[0036] The present invention differs from US 7048230B2 because US 7048230B2 does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the

[0037] 7

[0038] SUBSTITUTE SHEET (RULE 26) ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0039] US 6138955A disclosed a vortical lift over a highly swept wing that can be controlled by stabilizing or strengthening the major vortex by a small continuous jet of air, or a pulsating jet, near the core of the vortex. This method relies on the natural inductive action of the vortex swirling flow to entrain the injected air into the core of the vortex. When the additional momentum from the blowing air aligns with the vortex mean flow direction, the vortex is stabilized, and the vortex breakdown is delayed.

[0040] The present invention differs from US 6138955A because US 6138955A does not use the wingtip vortex core low-pressure area on the upper surface near the tip and the trailing edge to suck the boundary layer. US 6138955A requires a source of pressurized air to be ejected and uses the wingtip vortex core low-pressure area for mixing purposes, contrary to the present invention. Additionally, the present invention has an ellipsoid dome with an upward outlet, allowing the plenum to be exposed to the local pressure field of the external flow. The flow around the ellipsoid dome must accelerate, leading to a lower pressure per the Bernoulli principle at the upward outlet. Thus, much lower pressure is achieved inside the plenum to suck the boundary layer without experiencing a possible detrimental reverse flow.

[0041] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0042] Having described the invention in general terms, reference will be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0043] Figi shows a perspective view of a lift-generating body;

[0044] Fig 2 shows a perspective view of the lift-generating body;

[0045] 8

[0046] SUBSTITUTE SHEET (RULE 26) Fig 3 shows a top view of the lift-generating body;

[0047] Fig 4 shows a perspective view of the lift-generating body with the embedded plenum;

[0048] Fig 5 shows a perspective view of the lift-generating body with the embedded plenum;

[0049] Fig 6 shows a sideway view of the lift-generating body with the embedded plenum;

[0050] Fig 7 shows a perspective view of the ellipsoid dome with the reference frame;

[0051] Fig 8 shows a perspective view of the ellipsoid dome and the upper surface of the lift-generating body;

[0052] Fig 9 shows a top view of the ellipsoid dome;

[0053] DETAILED DESCRIPTION OF THE INVENTION

[0054] The present invention will be described more exhaustively hereinafter with reference to the accompanying drawings, in which some, but not all the embodiments of the invention are shown. Indeed, the invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that the disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0055] A lift is an aerodynamic force created by the relative motion between a body and a fluid. The body has a leading edge 3 and a trailing edge 4. The imaginary line directly connecting the leading edge 3 to the trailing edge 4 is called the chord. One surface 2 experiences a higher pressure than another surface on the body 1. This pressure gradient increases when the body's angle of attack, which is the angle between the direction of motion and the chord, augments until it reaches the critical angle of attack. At the tip of the body 5, a low-pressure area starts to develop within a vortex. That vortex will create an area of low pressure, which is strongest at its center, called the core. The core will move onto the upper surface 1 and achieve minimum

[0056] 9

[0057] SUBSTITUTE SHEET (RULE 26) pressure from surface 1 and the trailing edge 4 near tip 5. An ellipsoid dome 7, protruding from the upper surface 1 near the tip 5, extends into the wingtip vortex core. An outlet 8 on the ellipsoid dome 7, present in the wingtip vortex core, exposes the plenum 9 to the local pressure of the external flow. This local pressure in the vortex core creates a low-pressure area inside plenum 9 embedded in the lift-generating body. Any hole or slot 6 on the surface connected to plenum 9 will be an area of low pressure. When the pressure in plenum 9 is lower than the pressure on surface 1 at a location where a hole or slot 6 is present, part of the boundary layer on surface 1 will be sucked into plenum 9 and expelled at outlet 8.

[0058] The ellipsoid dome 7 is defined by the principal axes, the segments going between specific points. The first principal axis is the segment between points 10 and 13. The second principal axis is the segment going between points 11 and 12. Finally, the third principal axis is the segment between points 14 and 15. The length of the first principal axis is equal to a. The second principal axis length is equal to b. The third principal axis length is equal to c. Then the ellipsoid dome surface is defined by the equation

[0059] Any point on the surface satisfies this equation based on the reference frame.

[0060] For the present invention, all the principal axes are located at more than 70% length of the chord line. This means all the points 10, 13, 11, 12, 14, and 15 are located at a distance at least equal to 70% of the chord length from the leading edge and along a chord line. This is required to get the lowest pressure field at outlet 8 to relaminarize the airflow. The reference chord line to determine the 70% length is the chord line joining the last point on the leading edge to that last point on the trailing edge by moving toward the tip of the lift-generating body.

[0061] SUBSTITUTE SHEET (RULE 26) Furthermore, the external flow (created by the relative motion between the lift-generating body and a fluid) going around the ellipsoid dome 7 must accelerate, leading to a lower pressure at the outlet facing upward 8. Thus, a much lower pressure from the wingtip vortex core is achieved inside plenum 9 to suck and relaminarize the boundary layer. In the wingtip vortex, there is an axial flow component along the chord line that, by traveling around the ellipsoid dome 7, creates a much higher depression at outlet 8. This is due to the Bernoulli principle, comparable to a venturi effect.

[0062] Furthermore, there is a natural corrective effect of the pressure inside the plenum while varying the angle of attack. When the angle of attack increases, the pressure inside plenum 9 decreases because the vortex core at outlet 8 gets stronger.

[0063] The lift-generating body tip 5 can be rounded or curved to increase the wingtip vortex core's strength.

[0064] In specific cases, the pressure inside plenum 9 may be regulated for optimal performance at different speeds. For such circumstances, a valve system is added to plenum 9.

[0065] Also, riblets can be placed on surfaces 1 and 2 of the lift-generating body to reduce the drag and help suction the boundary layer at slot 6.

[0066] The present invention applies to wings, rotor blade, or winglets. Many systems like compressor blades, aircraft wings, wind turbines, or pumps are made of lift-generating bodies. This invention can enhance any device acting on a fluid.

[0067] SUBSTITUTE SHEET (RULE 26)

Claims

The invention claimed is :

1. An apparatus with a boundary layer relaminarization design by using an ellipsoid dome and a core of a wingtip vortex for a lift-generating body, the apparatus comprising: a lift-generating body with a tip (5) having no opening or slot or hole and one surface (2) experiencing a higher pressure than another surface (1); a leading edge (3) and a trailing edge (4); a hole or slot (6) placed on one of the surfaces of the lift -generating body; a plenum (9) embedded in the lift-generating body; an ellipsoid dome (7) protruding from the surface experiencing a lower pressure (1) of the lift-generating body, and located near the tip (5) and the trailing edge (4) having an outlet facing upward (8) which exposes the plenum (9) to the pressure field at the outlet (8) having the ellipsoid dome three principal axes and all the points (10), (13), (11), (12), (14), (15) located at more than 70% chord length from the leading edge and along a chord line and with the reference chord line to determine the 70% length being the chord line joining the last point on the leading edge to that last point on the trailing edge by moving toward the tip of the lift-generating body; characterized by when the lift-generating body is in relative motion in a fluid, the wingtip vortex core is located at the outlet (8), and that the flow in the wingtip vortex core moving around the ellipsoid dome (7) accelerates per the Bernoulli principle and a venturi effect is created at the outlet (8) further lowering the pressure at the outlet (8), creating a low-pressure field in the plenum (9) that is used to suck the boundary layer through the hole or slot (6).

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